Embodiments of the present invention relate to an assembling process for mounting a rolling bearing on a gear shaft. Gears having a shaft and two toothings which are axially distanced from each other and connected to each other by an intermediate portion of such shaft are well known. Gears of this type are coupled to a supporting structure by means of a pair of rolling bearings, which are mounted on opposite ends of the shaft, with two toothings arranged in intermediate positions between the bearings.
The need is felt to provide a gear which is more compact in the axial direction, in particular for applications in which it is used as planet gear in an epicyclic transmission.